1. Technical Field of the Invention
The present invention relates in general to the field of wireless telecommunications, and in particular, to a system and method for activating an optimum frequency hopping algorithm in real-time.
2. Description of Related Art
Mobile wireless communication is becoming increasingly important for safety, convenience, work efficiency, and simple conversational pleasure. One prominent mobile wireless communication option is cellular communication. Cellular phones, for instance, can be found in cars, briefcases, purses, and even pockets. To maximize the enjoyment of cellular phones, however, cellular wireless networks must be optimized.
Referring now to FIG. 1 of the drawings, an exemplary cellular wireless network, such as a Global System for Mobile Communication (GSM) Public Land Mobile Network (PLMN) 100, will be described. The PLMN 100 is composed of a plurality of areas 105, each with a Mobile Switching Center (MSC) 110 and an integrated Visitor Location Register (VLR) 115 therein. The MSC/VLR areas 105, in turn, include a plurality of Location Areas (LA) 120, which are defined as that part of a given MSC/VLR area 105 in which a mobile station (MS) (terminal) 125 may move freely without having to send update location information to the MSC/VLR area 105 that controls the LA 120. Each LA 120 is divided into a number of cells 130. Mobile Station (MS) 125 is the physical equipment, e.g., a car phone or other portable phone, used by mobile subscribers to communicate with the cellular network 100, each other, and users outside the subscribed network, both wireline and wireless.
The MSC 110 is in communication with at least one Base Station Controller (BSC) 135, which, in turn, is in contact with at least one Base Transceiver Station (BTS) 140. The BTS is the physical equipment, illustrated for simplicity as a radio tower, that provides radio coverage to the geographical part of the cell 130 for which it is responsible. It should be understood that the BSC 135 may be connected to several base transceiver stations 140, and may be implemented as a stand-alone node or integrated with the MSC 110. In either event, the BSC 135 and BTS 140 components, as a whole, are generally referred to as a Base Station System (BSS) 145.
With further reference to FIG. 1, the PLMN Service Area or wireless network 100 includes a Home Location Register (HLR) 150, which is a database maintaining all subscriber information, e.g., user profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information. The HLR 150 may be co-located with a given MSC 110, integrated with the MSC 110, or alternatively can service multiple MSCs 110, the latter of which is illustrated in FIG. 1.
The VLR 115 is a database containing information about all of the Mobile Stations 125 currently located within the MSC/VLR area 105. If a MS 125 roams into a new MSC/VLR area 105, the VLR 115 connected to that MSC 110 will request data about that Mobile Station 125 from the HLR database 150 (simultaneously informing the HLR 150 about the current location of the MS 125). Accordingly, if the user of the MS 125 then wants to make a call, the local VLR 115 will have the requisite identification information without having to reinterrogate the HLR 150. In the aforedescribed manner, the VLR and HLR databases 115 and 150, respectively, contain various subscriber information associated with a given MS 125.
Each MS 125 is affected by a myriad of signal-degrading phenomena. For instance, small-scale fading (also called multipath, fast, or Rayleigh fading) creates peaks and valleys in received signal strength when the transmitted signal propagates through terrain populated with signal-reflecting structures. A second signal-degrading phenomenon, large-scale fading (also called log-normal fading or shadowing), reduces received signal strength when the transmitted signal is degraded by large objects (e.g., hills, building clusters, forests, etc.). A third signal-degrading phenomenon, co-channel interference, reduces the ability of an MS 125 to correctly receive a desired signal from a first BTS 140 because an undesired signal from a second, more distant, BTS 140 is interfering. Many other signal-degrading phenomena (e.g., path loss, time dispersion, and adjacent channel interference) adversely impact wireless communications.
Fortunately, many techniques have been developed to combat these signal-degrading phenomena. Some examples are channel coding, interleaving, equalization, antenna diversity, and frequency diversity. Frequency diversity has several possible implementations, one of which is frequency hopping (FH). Furthermore, FH can be instituted with many different algorithms. Only one of the many FH algorithms is instituted within any one cell 130 in existing systems. Conventionally, in fact, the type of FH algorithm is selected when the system is designed. Unfortunately, the optimum FH algorithm can vary depending on current conditions within the cell 130. In summary, existing systems have heretofore only instituted a single FH algorithm within any given cell.